The present invention generally relates to wireless communication networks, and particularly relates to multi-sector transmission in such networks.
Some types of wireless communication networks, such as cdma2000, employ a form of diversity transmission known as soft handoff, on forward and/or reverse links between the network transmitter(s) and a targeted subscriber. In soft handoff, the same data is transmitted from two or more sectors, and such transmission is particularly useful in maintaining the subscriber's data connection as the subscriber moves between radio sector coverage areas in the network.
However, in some types of networks, soft handoff is not used, at least for some types of channels. For example, in the 1xEV-DO Rev. A standards, each sector transmits a high-rate shared packet data channel. Multiple subscribers in each sector share the channel according to time-scheduled transmissions managed by a scheduler that typically resides at the physical layer within the base station transmitters being used to serve the sector. Service for a given subscriber is scheduled according to an overall scheduling objective, the subscriber's needs, etc. When the subscriber moves to another sector, the data for that subscriber generally is redirected to the scheduler in that new sector.
Of course, some of the evolving transmission protocols employ spatial transmit diversity for higher-rate packet data services, wherein the same data is transmitted from different antennas, or employ spatial transmit multiplexing, wherein different data for the same subscriber is transmitted from different antennas for a higher aggregate data rate. Various approaches to multiple-input-multiple-output (MIMO) and multiple-input-single-output (MISO) systems represent examples of systems where spatial multiplexing is used to achieve higher aggregate data rates.